1. Field
Exemplary embodiments of the present invention relate to a semiconductor device, and more particularly, to a method for removing a defect of a metal layer and a method for fabricating a semiconductor device using the same.
2. Description of the Related Art
With the increase in integration degree of a semiconductor device, the difficulty level in fabricating the semiconductor device has also increased to approach its limit. DRAM, for example, may decrease the thickness of a high-k dielectric layer with the increase in the integration degree. Accordingly, a serious leakage current may occur. The leakage current is significantly affected by properties and interface defects of a metal layer as well as the dielectric layer forming a capacitor.
FIG. 1 is a transmission electron microscopy (TEM) photograph showing a metal layer of a conventional capacitor.
Referring to FIG. 1, the surface roughness of titanium nitride used as the metal layer of the capacitor is high, and uneven poly-crystal grains and micro-defects are found.
In particular, in a stacked structure of a high-k dielectric layer and a metal layer, the layers may contain a lot of defects and impurities occurring during a layer formation process. The defects and impurities may cause a secondary consideration.
FIGS. 2 and 3 are cross-sectional views illustrating features of a conventional stacked structure of the metal layer and the high-k dielectric layer.
Referring to FIG. 2, defects such as dangling bonds may be formed in the metal layer during the layer formation and easily react with oxygen contained in the high-k dielectric layer. Accordingly, the oxygen escapes from the high-k dielectric layer to make vacancy defects inside the high-k dielectric layer. As a result, a leakage current occurs.
Referring to FIG. 3, a metal layer having a columnar structure has low energy at a grain boundary in a vertical direction, and the metal layer provides a path through which oxygen escapes much more easily. Accordingly, defects may increase. Furthermore, a large amount of carbon contained in the high-k dielectric layer and the metal layer easily reacts with oxygen, and the oxygen easily escapes through the grain boundary. Therefore, the occurrence of oxygen vacancies is accelerated. As a result, a leakage current occurs.
In order to improve the property of the metal layer or the high-k dielectric layer, a heat treatment is performed after the metal layer is formed. However, during the heat treatment, the occurrence of oxygen vacancies may be accelerated. Accordingly, even if the heat treatment is performed at an oxygen atmosphere to suppress the occurrence of oxygen vacancies, interface oxidation may occur due to permeation of the external oxygen. In this case, resistance may increase.